The overall goal of this project is to elucidate the mechanisms of action of the chlorinated hydrocarbons: trichloroethylene, hexachlorobenzene, and a polychlorinated biphenyl mixture. These environmental chemicals are recognized as immunosuppressive, yet little is known concerning their inhibitory mechanisms. We propose using the Mishell-Dutton assay, an in vitro system for antibody prodiction, to elucidate the inhibitory mechanisms of these chlorinated hydrocarbons. A microsomal system for metabolic activation will be incororated into the assay during the initial phase. This phase will invlove characterization and standardization of the modified Mishell-Dutton assay, using methyl-nitro-nitrosoquanindine and cyclophosphamide as positive controls, the former direct-acting and the latter requiring metabolic activation. As these chemicals are studied, techniques for separation of the cell populations invloved will be developed. Following the initial dose-response, temporal, and reconstitution experiments with the test chemicals, the techniques will be brought to bear on the chlorinated hydrocarbons, incorporating the activation system if its inclusion affects the activity of the compounds. During this phase of the work, we will look for the best system for activating these chlorinated hydrocarbons by trying various inducers of mixed function oxidases. We will then attempt to define the cell type, stage of development and cellular site of action of the three chlorinated hydrocarbons. Overall, the proposed evaluation an utilization of modified Mishell-Dutton assay should clarify the applicability of this system to the area of environmental immunotoxicology as both a screening assay and a tool for elucidation of mechanisms of immunosuppression by other environmental chemicals.